Products containing the active ingredient imidacloprid (Bayer Advanced Tree & Shrub Insect Control, Bonide Annual Tree & Shrub Insect Control, Ferti-lome Systemic Tree & Shrub Drench, Green Light Tree & Shrub Insect Killer, etc.) are available to homeowners for do-it-yourself protection of ash trees against attack by the emerald ash borer (EAB). Green Light Tree & Shrub Insect Control with Safari (dinetofuran) also is an option. Annual applications should be made between late March and late April according to label directions. The treatments can help to protect trees up to 60 inches in circumference (measured at 4.5 feet above the ground.) Larger trees require injection of insecticides available only to licensed commercial applicators. Protective treatments are suggested only for ash trees within 15 miles of known EAB infestations or for trees within quarantined counties.
Figure 1. Counties in green comprise the current EAB quarantine area in KY.
Consider several factors when making treatment decisions: tree location, health, value, treatment cost, and removal/replacement expense. There is no consensus as to how long treatments may be needed. However, it is likely that trees will need to be protected for at least 5 to 7 years as the EAB infestation sweeps through an area. Untreated ash trees will serve as sources of beetles. You can get an idea of the number in your county from this inventory: http://pest.ca.uky.edu/EXT/EAB/Ashnumbers.pdf. Numbers of stems per county range from over 6.8 million in Henry County to just over 38,000 in Martin County. The larger the population of ash trees, the longer and more intense the infestation is likely to be.
The polar vortex probably was no help against the EAB in Kentucky. The borer is a hardy insect that spends the winter as a full-grown larva in a cell formed in the outer sapwood. Winter survival in a U.S. Forest Service experiment near St. Paul, MN (air temperature of minus 18.4° F for about 5 1/2 weeks) resulted in about 40% mortality. The researchers also learned that standard weather station temperature readings are not accurate indicators of those affecting larvae in their overwintering cells due to factors such as radiant warming on sunny days. It is unlikely that our 2013-2014 winter contributed significantly to natural EAB mortality.
by Lee Townsend, Extension Entomologist